# Graphx Example 2

### pageRank example

Given user data in users.txt and follower data in followers.txt, with the column name is as illustrated, calculate pageRank with tolerence at 0.0001 for each user, sort the output by rank.

### users.txt (user id, username, name)

```
1,BarackObama,Barack Obama 
2,ladygaga,Goddess of Love 
3,jeresig,John Resig 
4,justinbieber,Justin Bieber 
6,matei_zaharia,Matei Zaharia 
7,odersky,Martin Odersky 
8,anonsys
```

### followers.txt: (follower user id, to be followed user id)

```
2 1 
4 1 
1 2 
6 3 
7 3 
7 6 
6 7 
3 7
```

Code:

```
import org.apache.spark._
import org.apache.spark.graphx._
import org.apache.spark.rdd.RDD
import org.apache.spark.graphx.GraphLoader

// Load the edges as a graph
val graph = GraphLoader.edgeListFile(sc, "file:///home/dv6/spark/spark/data/graphx/followers.txt")
// Run PageRank, with 0.0001 as tolerence 

val ranks = graph.pageRank(0.0001).vertices

ranks.foreach(println)
/*
user id, ranking
(4,0.15007622780470478)
(6,0.7017164142469724)
(2,1.3907556008752426)
(1,1.4596227918476916)
(3,0.9998520559494657)
(7,1.2979769092759237)
*/

// Join the ranks with the usernames
val users = sc.textFile("file:///home/dv6/spark/spark/data/graphx/users.txt").map { line =>
  val fields = line.split(",")
  (fields(0).toLong, fields(1))
}
val ranksByUsername = users.join(ranks).map {
  case (id, (username, rank)) => (username, rank)
}

ranksByUsername.foreach(println)

/*
Output:
(BarackObama,1.4596227918476916)
(jeresig,0.9998520559494657)
(odersky,1.2979769092759237)
(justinbieber,0.15007622780470478)
(matei_zaharia,0.7017164142469724)
(ladygaga,1.3907556008752426)

*/

//Sortby ranking

ranksByUsername.toDF.withColumnRenamed("_1","username")
         .withColumnRenamed("_2","rank")
          .createOrReplaceTempView("ranksByusername")
spark.sql("select * from ranksByusername order by rank desc").show()
/*
Output:
+-------------+-------------------+
|     username|               rank|
+-------------+-------------------+
|  BarackObama| 1.4596227918476916|
|     ladygaga| 1.3907556008752426|
|      odersky| 1.2979769092759237|
|      jeresig| 0.9998520559494657|
|matei_zaharia| 0.7017164142469724|
| justinbieber|0.15007622780470478|
+-------------+-------------------+



*/
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://george-jen.gitbook.io/data-science-and-apache-spark/graphx-example-2.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.